Hereby I'm selling my HD600. I bought them from someone else, but after a month I have decided that I rather have closed cans.
A few things to note:
1- The headphone needs a new cable. After I repaired the damaged cable I tried to reinforce it, but sadly I broke it in the process, the irony still hurts me. Sennheiser sells new HD650 cables for €12, excluding the €5 shipping.
2- The earpads are soft, I tried to replace the foam, but I don't really have any decent foam to replace it with. Youtube has a nice tutorial on how to do it with memory foam. Do note: they are still very comfortable, but the short distance from the driver kind of diminishes the sound stage and adds extra pressure. A new pair of pads costs €43 on Sennheisers site, excluding the €5 shipping.
3- I put different foam in the headpad, cause it was flat, it does it's job quite well, but it still has to soften up a bit. A new one costs €9 excluding the €5 shipping.. on.. you guessed it.. Sennheisers site.
4- The top logo has a lot of scratches and chipping, the right logo is non-existant, (I removed it because it was simply unreadable) and the left logo is 100% mint. I don't really care for the aesthetics, but if I would remove the top logo it would -look- like new, while still having one logo to keep it proffesional. A silver marker could do the trick too, (but I wouldn't want to risk a mess.)
By the way, all these problems are sort of common on the HD600s, but the sound is sublime like always.
My price is €120 (shipping excluded), I think that's a pretty decent price, considering a pair of HD600 drivers run for the same price, and that doesn't include the grid covers, headband and the pads. even with a new cable and new head- and earpads it would cost only €189, which is still a bit cheaper then the average second handed price.
You can always PM me if you have any questions.